This invention relates to two-way radio communications systems in generally and particularly to a system in which communication cells can have different operating characteristics.
In a conventional cellular type two-way radio communication system, when a roving radio such as a portable or mobile radio moves from one location to another it is often necessary to transfer or hand-off the radio from one cell to another. In a cellular type system, rather than having a single universal coverage area, smaller areas or cells are covered by one or more base stations. Typically adjacent cells operate on different frequencies to avoid interference. In conventional cellular telephone systems, as a roving station moves between cells, it is necessary for a central controller to instruct the roving radio as to which frequency it should move in order to access another cell for reliable communication. In order to do so, the control station has to determine which cell has the best communication with the roving station. This is done essentially by a voting arrangement where different cell receivers report on the strength or quality of the roving radio signal and the central station accordingly assigns the roving station to a communication cell. While such an approach does provide for cell hand-off, it requires a substantial intrastructure investment and complexity. There must be receivers for determining received signal strength at each cell, all of which must be linked back to a central station, which must determine the appropriate cell for communication with the roving station. It would be desirable for the roving station to make the cell hand off determination thereby, obviating the substantial infrastructure investment required for the decision to made by the control station.